In the previous post, you have learned about ACID properties of the database transactions for traditional databases. As transactions are growing over the internet, systems are scalable and distributed. In some of the systems where availability is more important than the consistency.

For Example, Amazon, eBay, etc.

For such types of systems in 2000, Eric Brewer’s introduce a theorem that’s called CAP Theorem. It states that

“In a distribution system can only have two out of following three Consitentency, Availability, and Partition Tolerance- One of them must be a sacrifice. You can’t promise all three at a time across reading/write requests.”

Based on CAP theorem, where scalability and availability is most important. It introduces alternatives to ACID is BASE for distributed database transactions.

BASE full form:

Basically Available

The system guarantees availability.

It majorly focuses on availability, potentially with outdated data and it does not provide guarantee on global data consistency across the entire system.

Soft-state

The state of the system may change over time.

Even without explicit state updates, data may change due to the asynchronous propagation of updates and nodes that become available.

Eventual consistent

The system will eventually become consistent.

Updates eventually propagated, the system would reach in a consistent state if no further updates and network partitions fixed.

See Also:

• ACID vs BASE for Database Transactions
• ACID Properties for Database Transactions
• CAP Theorem